Hello,
I did a fresh install of the latest v1.4 release on Win10 to a local disk F instead of C. Mbed Studio was installed to F, it created %User% folder on F, but kept it almost empty and downloaded all the stuff (mbed-os and other files) to %User% folder on C. As the result I have 750Mb on F and 6(SIX!)Gb on C. And 1Gb+ mbed-studio-updater in AppData on C